1. Field of the Invention
The present invention relates generally to systems for leak detection in storage tanks. More specifically, the present invention relates to a differential pressure measurement system which detects fuel leaks from underground and aboveground storage tanks.
2. Description of the Prior Art
Currently, there are a large number of underground as well as above aboveground fuel storage tanks which potentially pose a significant environmental threat to groundwater and land resources worldwide. Leaking fuel storage tanks, left undetected, can contaminate large volumes of soil and ground water and require substantial resources and financial expenditures to clean up. Early detection of a fuel leak is necessary to minimize the environmental impact to soil and groundwater resulting from leaking fuel.
There are numerous types of fuel leak detection systems currently available to detect fuel leakage from an underground or aboveground storage tank. Volume based fuel leak detection systems measure the fuel level and fuel temperature in the tank. Temperature measurements are needed to compensate for fuel volume changes caused by temperature changes within the tank. A loss in temperature compensated fuel volume is an indication of a fuel leak.
Mass based leak detection systems measure the mass of fuel in the tank by measuring pressure near the bottom of the tank. Mass based detection systems are not affected by changes in the temperature since changes in temperature do not affect the total mass of fuel within the tank. Thus, the inaccuracies and cost associated with temperature measurements are avoided.
However, pressure measurement leak detection systems have limitations. For large bulk storage tanks, even with highly accurate pressure gauges, significant errors in detecting fuel leaks will occur. For example, a 250 feet deep by 100 feet diameter fuel tank generates a pressure of approximately 80 psi at the tank bottom. A high precision pressure transducer, which can detect a 0.01 psi change over full scale (precision=0.0125%), will have an approximate 2,200 gallon error for this size tank.
In addition, tank mechanical configurations, atmospheric conditions and ventilating systems can create differences in vapor pressures in upper tank above the fuel and lower tank areas. In large fuel storage tanks, these variations can cause several thousand gallon errors in leak detection systems.
Accordingly, there is a need for a highly accurate and reliable, yet relatively simplistic fuel leak detection system for use in large fuel storage tanks which overcomes the above-identified limitations of currently available pressure measurement fuel leak detection systems.